The present invention relates to multiple ply packaging materials, and in particular to multiple ply packaging materials having exceptionally high gas barrier properties.
Thermoplastic films have gained wide acceptance in the packaging industry, and are commonly employed to package foods in both liquid and solid form. Many thin films composed of polymeric materials, however, while having excellent liquid impermeability characteristics, are highly pervious to oxygen and other gases such as carbon dioxide. A pouch composed of polyethylene, for example, allows relatively rapid penetration of atmospheric oxygen and other gases into the interior thereof, in comparison to containers made of metal or glass.
In the packaging of many food and other products which are sensitive to or reactive with oxygen, it would be desirable to provide a packaging or container material which has the versatility and liquid impermeability of a polymer, and yet has excellent gas barrier properties. The contamination of food products with oxygen after packaging often has many undesirable effects, including discoloration, deterioration and spoilage of the product, as well as significant loss in acceptable shelf storage life.
An exemplary embodiment of a polymer packaging material which has improved gas barrier properties is disclosed in my pending application Ser. No. 597,761, now U.S. Pat. No. 4,105,818. As taught therein, it has been discovered that the provision of certain vinyl and other polymeric films in multiple ply form unexpectedly and significantly increases their gas barrier properties, or decreases their gas permeability, in comparison with a single ply film of the same material and same overall thickness, beyond that expected from thickness considerations alone. Nevertheless, to optimally protect certain products against the detrimental effects of oxygen and/or other gases which may still pass through a polymer film in multiple ply form, it would be extremely desirable to provide a packaging material which exhibits the advantages and versatility of a polymer, and yet has exceptionally great gas barrier properties.